The present invention relates generally to a single-use disposable needle-free (or needleless) jet injection device. Specifically, this invention relates to such a jet injection device that comprises a hand-held injector having a pre-filled drug cartridge sealingly carrying injectable drug, a sealed cylinder of pressurized gas, a piercing mechanism for penetrating the gas cylinder, and a trigger device for releasing the discharge mechanism. The device is smaller and has fewer parts than prior disposable systems, and can be easily assembled and filled using automated equipment.
Needle-free or needleless hypodermic jet injection devices have been in commercial use for over 40 years. A number of these devices have used pressurized gas to power a hypodermic jet injection. The related technology includes a number of teachings for gas-powered injection devices, including: U.S. Pat. No. 4,596,556, issued to J. Thomas Morrow, et al.; U.S. Pat. No. 4,913,699, issued to James S. Parsons, and U.S. Pat. No. 5,730,723, issued to Thomas P. Castellano, et al. WIPO publication WO 97/37705 also discloses a gas powered disposable needle-free hypodermic jet injector.
The Morrow, et al. ""556 patent is believed to teach a reusable hypodermic jet injection device in which a housing receives a shell or cartridge having a bore leading to a discharge aperture. Within the bore is received both a plunger sealingly engaging the bore, and a pressurized gas cylinder that rests against the plunger. The injection device includes a ram having a penetrating tip confronting a penetrable wall section and seal of the gas cylinder, and a discharge mechanism for driving the ram through the penetrable wall section of the gas cylinder when a trigger device is released. Discharge of the pressurized gas from the cylinder drives the plunger to effect a jet injection, and also drives the seal of the gas cylinder to effect resetting of the discharge mechanism. The shell with its plunger and spent gas cylinder is discarded after an injection; a new shell, pre-filled with medication and with a new gas cylinder, is used for each injection.
The Parsons ""699 patent is believed to teach a single-use jet injector that is discarded after one use. This injector is believed to have a body with a pair of gas chambers separated by a breakable valve. One of the gas chambers contains a pressurized gas, while the other chamber is sealingly bounded by a piston that drives a plunger. The plunger sealingly bounds a chamber into which a dose of medication is loaded by the user before the injection. This medication dose chamber leads to an injection orifice so that when the valve is broken, the piston and plunger are moved by pressurized gas communicated to the second chamber, and the plunger drives the medication forcefully out of the injection orifice to form an injection jet. After a single use, the device is discarded.
The Castellano ""723 patent, which was issued in 1998 and which does not cite the earlier Parsons ""699 patent, is believed to teach substantially the same subject matter as Parsons et al.
WIPO publication WO 97/37705 published pursuant to a Patent Cooperation Treaty (PCT) application for joint inventors Terence Weston and Pixey Thomlea, is believed to disclose a disposable hypodermic jet injector in which the device is powered by a gas pressure spring of the type common in the tool and die art as a substitute for the conventional metal spring-powered ejector pin. In the Weston device, the ram of the gas pressure spring is held in a contracted position by a trigger mechanism. When the trigger mechanism is released, the gas pressure spring is supposed to expand and drive a piston sealingly received in a bore and leading to a fine-dimension orifice to produce a jet hypodermic injection from liquid held in the bore ahead of the piston.
The Weston device is thought to have several deficiencies such as difficult and costly manufacturing and sterilization processes because the pressurized gas and a drug dose need to be contained in the same package, and a possible inability to endure long-term storage while still retaining the gas pressure in the gas spring. In other words, the gas pressure spring of the Weston device contains only a small quantity of gas, and depends upon the sealing relationship of the ram of this spring with a cylinder within which the ram is movably and sealingly received in order to retain this gas pressure. Even a small amount of gas leakage over time will be enough to render this injector inoperative.
It also is known in this art to provide a needle-free injection system having two plungers that are initially spaced adjacent either end of a glass drug storage sleeve, with liquid drug being disposed between the plungers within the sleeve. Such a system also includes a plastic drug storage chamber disposed coaxially with and forwardly of the glass drug storage sleeve. The forward end of the plastic drug chamber terminates in an injection orifice. The plastic drug chamber includes an enlarged portion that permits drug to flow past the forward plunger when that plunger is aligned with the enlarged portion.
In this earlier system, axial force is exerted on the rear plunger immediately prior to injection. Because liquid drug is disposed in the space between the plungers, the plungers move in unison in a forward direction until the forward plunger is aligned with the enlarged portion. At that point, the continued forward travel of the rearward plunger forces liquid drug around the forward plunger until all of the drug is disposed in the plastic drug chamber forward of both plungers, which are now in abutment. The unit thus is ready for actuation.
When the unit is actuated the plungers both exert a forward axial force, causing liquid drug to be directed out of the injection orifice and into the patient.
One form of the invention provides a needle-free injection system including the following components: a nozzle portion having a glass wall defining a drug storage space, and an injection wall defining a drug injection space, the injection wall being coaxial with the glass wall and defining a plurality of drug bypass conduits disposed adjacent a forward end of the drug injection space; a body portion mounted to the nozzle portion such that relative axial movement may be effected between the portions; an injection orifice defined at the forward end of the injection space; a drug plunger defining a rearward end of the storage space; a drug plug initially disposed between the storage space and the injection space, and being displaceable into the injection space adjacent the bypass conduits; and a pierceable gas cartridge for providing injection power to the drug plunger.
Another form the invention takes is a needle-free injection system including the following components: a nozzle portion defining a forwardly-facing injection orifice; a body portion mounted to the nozzle portion, the portions being displaceable toward each other to prepare the system for actuation; and a safety tab for preventing actuation prior to the time that relative displacement is effected between the nozzle portion and the body portion, the safety tab being fragibly mounted to one of the body portion or the nozzle portion and including a contact part, the safety tab to be contacted and broken when the portions are displaced toward each other.
Yet another form the invention takes is a method for preparing a needle-free injection unit for injection, comprising the following steps: providing a storage compartment for liquid drug; positioning an injection orifice forwardly of the storage compartment, through which the liquid drug is selectively injected into the patient; providing a pressurized, pierceable gas storage cartridge with a system for conveying pressure to the storage compartment when the cartridge is pierced; positioning a seal between the cartridge and the storage compartment to prevent gas pressure from reaching the storage compartment after the cartridge is pierced, but prior to actuation of the unit, the seal being positioned such that the piercing of the cartridge provides axial pressure on the seal; providing a trigger having a roller positioned such that when axial pressure is provided on the trigger, an outward force is exerted on the trigger; and positioning a trigger actuator outwardly of the trigger to prevent the trigger from moving outwardly until the unit is actuated.